easy solution - just change the file extension form .MDF to .ISO (When you click on the file name like you're going to rename it, just replace .MDF with .ISO). This will make the file appear to be a disk image. I just recently had a video file that a friend gave to me like this...and once I converted it (by changing the file extension), I just opened up the DVD player (in OS X) and started watching it. I'm sure you could use the disk utility to burn it. I would probably use Toast, or Visual Hub instead - but then again, disk utility is free.
Hope this helps.
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"Talk is the same cheap...it's been..." - JM